Method of electric welding



H. A. WOOFTER METHOD OF ELECTRIC WELDING March 9 1926i 1,576,169

Filed Feb. 5, 1925' I N VEN TOR. Herberf A. We offal:

- B? IWMQUZL Patented Mar. '9, .1926.

. UNITED "STATES 1 1,576,169 PATENT OFFICE.

HERBERT ADDISON 'WOOFTEB, OF BWAIPSCOTT, MASSACHUSETTS, ASSIGNOR TO THOMSON ELECTRIC WELDING COMPANY, OF LYNN, MASSACHUSETTS, A (30330- TION OF MASSACHUSETTS.

warrior or nmc'rnic WELDING.

application filed February 3, 1825. Serial No. 8,515.

Be it known that I, HERBERT A. WoOrmn, a' citizen'of the United .States, and a resident of Swampscott, in the county of ,Essex and State of Massachusetts, have invented certain new and useful Improvements in Methocls of Electric Welding, of which the following is a'specification.

This invention relates to a method of and apparatus for electric welding and more particularly to methods-and apparatus of such character that as the welding progresses the reactance ofthe work upon the conductor supplying current to. the weld in-' creases so as to absorb the'electricpower and thereby cause a difi' erenc'e in the amount of welding current at the beginning and at the end' oi the welding operation.

The invention is designed particularly for use in a method of and apparatus for electric seam welding, and its utility and prin- 'ciple of action will behest understood by reference to a. cominon form of electric seam welder "wherein the welding electrode is former.

mounted upon a suitable movable carriage or, support and moves over the work in producing the seam, while its connection with the source of'welding current is maintained by sliding connection of said electrode with a rail' or support extending out over the work and itself joined at one end to the source of welding currentsuch for instance as vthe lower tension secondary of a trans- 4 In a common form of this apparatus a roller welding electrode is employed and is mounted on a movable-carriage w ich slides against a fixed upper electrode horn form- .ing the upper member of the gap inwhich the, work is arranged, so that as the roller electrode moves-out from the beginning of the seam toward the end thereof the length of conductor travensedby the electric weldin'g current becomes longer and therebythe power tends to; drop oil is the electrode '3 moves.

In addition to the drop {of power attrib+ ut'able to the increase of length and react-* ance drop of the conductor itself, there is a drop in power. due to the-fact that as the roller or electrode moves, more and more of the work'. assumes a reactive or inductive relation to the conductor carrying the current so that r gh h s cha ge of rel tion .of the 'work to the conductor a further re- The practical result of these actions is that if the current be adjusted for starting the seam properly there will be a'tendenc'y to drop in welding current orpower as the work progresses and with a seam of considerable length the current will be insufli cient or. unsuitable for the best welding results at the end of the seam.

The aim pf my invention is to secure a practical] throughout the -eration by. properly'compensa'ting for the drop due to change of reactance of-the work or resistance in the supply conductor, one or both, as the work progresses. To accomplish this result Ipropose to automatically change the inductive relation of that element of the generator in which the welding current is produced by induction in a magnetic field, for directapplication tov the work, and progressively and in accordance with the progress of the work and in such manner-that the power of the current genuniform welding current progress of the welding operated will increase as thetendency to drop in current, from the causes' above mentioned increases.

employ as a current generator a suitable welding transformer and to connect the low.

' such a manner that a's'the'machine elements move a corresponding movement will be'iinparted to the'current generating portion of said seconda i and in such a way as to :chan itsin uctive or effective generating position in the transformer fiel'd and increase the electroniotive force. v

Preferably the current enerating portion of saidsecondary so emp oyed is a loop or turn thereof. so arranged with relation to the magnetic field or core of the transformer that the effect of-movin the same by'its connection with the 'mova 1e element'of the welder will be tocontract the loop or turn and thereby bring it into more effective 0 better magneti relation withrespect to t e transformer fie d as the electrode movesq In the accompanying drawings: Fig. 1 shows in side elevation the essential lem nts 01 to apparatus in which my n.

a In carrying out my invention I prefer to vention may be realized, the parts being shown in position corresponding to the beginning of a seam welding operation.

Fig. 2 shows the same parts at the end of the welding operation.

In said drawings v I 1 indicates the fixed lower or work sup} porting horn of-a seam welder and 2 indicates a piece of work supported thereon and consisting for instance of a cylinder of sheet metal to be completed by welding of the.

overlapping or juxtaposed edges of the metal sheet along the section or line 3. As

will bewell understood two plates or sheets which is indicated at 8 while'the primary is indicated at 9. The secondary loop or gencrating coil at its end opposite the welding electrode is fastened in welding connection with the metal support or bracket 10 carrying the horn 1 in the usual manner. 'As

will be seen. the flexible secondary loop or.

semi-turn is so arranged-that at the beginmug of the welding operation avery con- I siderable air gap or space 11 between it and-the core 8 is afforded, but when the electrode 6 1s moved to-the endof the seam as I shown in Fig. 2 said loop will be contracted or drawn in with conse uent decrease of said air gap and with a resu ting change in positlon of the secondary element of the trans-- former with relation to theotherelements such that an increase inelectro -motive'force or current output from saidv generator will result. This increase of electro-motive force takes place progressively as the electrode' moves and substantially in accordance with the decrease of output due tothe-lengthening of the secondary terminal as well as .to the increase of--react1on of work as itcomes in reactive relation to the portion of generatingconductor above it. The proportion or relation of the parts may be'made such that when the electrode is short-circuited in the position 6 without any work in. the horn and again in posit-1on5 and readings taken at each point, they maybe made to show 30. percent'les's power output at 6 than at llGll is the condition desired forno load condition. When however the work is in sorted and the weld made by moving the electrode from 6 to 5, the instruments will show practically little or no drop as the welding progresses and the power curve be- "comes practically a horizontal straight line, the fork. gradually being introduced in the have been t 1e rise in the horn havin absorbed what-otherwise wouldower curve. The travel of the electrode an the movement of the u per part of the secondary winding may e accomplished by any of the approved methods, such as by belt drive or motor suitably geared, and. the primary winding and core of the transformer 0 erate in accordance with established wel ing transformer'practice.

As will be obvious it results that when the weld is started the current may be such that there will be no burning at the start as has been the case in the past and the current will be sufficient to produce a proper weld, while astheelectrode moves out along the work from position shown in Fig. 1 to position shown in Fig. 2 and the air gap or loop 11 is decreased there will be a progressive increase-of electro-motive force tending to increase the power of, the welder progressively so that the drop due to the changing position of the welding electrode and work with relation to one another will be compensated for and an approximately constant welding current attained.

What I cla-im'as my invention is 1. In an electric seam welding apparatus wherein a movable electrode has a flexible terminal of the secondary irectly attached to and sup lying current t said electrode, the meth the length 0 seam increases consisting in. automatically decreasingthe air gap between a portion of said-flexible secondary and the transformer core to automatically consisting in flexing a loop or turn of the secondary in the magnetic. field of the transformer coincidently with thc movement of the ele trode'so as toincreasethe electromotive iorce in a manner to obtaina practically constant welding current in all positions of the electrode.

' In the rt of electric seamwelding'Khy low tension c rent derived from a tr usof com ensating :for the in- .creas'ed absor tion 0 power by the work as former and applied by means of an electrode in contact with the work, the method of compensating for the-dre p in power as the welding proceeds, ,consistmg incontracting or drawing in the secondary with relationto the magnetic field. to .increase the electro-' motive force and secure a substantially constan't output of welding-current at the Weld in all positions of said electrode on the seam. Signed at Lynn, in .the county of Essex' and State-of Massachusetts, this-28th day i of January All 1925'.

HERBERT ADDISQN WOOFTER. 

